the 2010 oil spill in the Gulf of Mexico deva
the 2010 oil spill in the Gulf of Mexico devaReuters

British energy giant BP on Tuesday vowed to "vigorously defend" itself in court next week over US government claims for "excessive" fines linked to the 2010 Gulf of Mexico oil spill disaster.

"BP will vigorously defend against gross negligence allegations," the energy giant said ahead of the start of a federal civil trial on Monday, AFP reported.

BP returns to the Louisiana courthouse on February 25 for a mammoth trial consolidating scores of remaining lawsuits stemming from the worst environmental disaster to strike the United States.

The energy major must also still resolve a civil case on environmental fines which could amount to as much as $21 billion if gross negligence is found. It also remains on the hook for billions in economic damages, including the cost of environmental rehabilitation.

"We have always been open to settlements on reasonable terms, failing which we have always been prepared to defend our case at trial," said Rupert Bondy, Group General Counsel at BP, in a company statement.

"Faced with demands that are excessive and not based on reality or the merits of the case, we are going to trial.

"We have confidence in our case and in the legal team representing the company and defending our interests."

The group on Tuesday added that it believed the official US government estimate of 4.9 million barrels of oil spilled into the sea was "overstated" by at least 20 percent.

"BP believes that a figure of 3.1 million barrels should be the uppermost limit of the number of barrels spilled that should be used in calculating a Clean Water Act penalty," it said.

The blast on the BP-leased Deepwater Horizon drilling rig on April 20, 2010 killed 11 people and unleashed millions of barrels of oil into the Gulf, blackening beaches in five states, and crippling tourism and fishing industries.

Last month, a US judge approved a $4.5-billion deal in which BP pleaded guilty to criminal charges from the devastating spill.